Hello, the answer is C and this is because if you subtract 2640 from 5280 you get 2640. Now if you add 2640 to 5280 you get 7920. But this answer does not work because it is way too small, therefor you will need a larger number and if you add 2640 to 10560 you get exactly 13200. Sorry if I’m wrong, best of luck.
